Recent research in our laboratory shows that rats acutely (2 hrs) exposure to a 60-Hz magnetic field (0.1 - 0.5 mT) have an increase in DNA single and double strand breaks in their brain cells. Experiments are proposed to further investigate the mechanism by which exposure to a 60 Hz magnetic field causes DNA damages in brain cells of the rat. Specifically, the role played by free radicals will be investigated, since our preliminary research also shows that treatment of rats before exposure with free radical scavengers (melatonin and a spin trap compound) can block the DNA damaging effect of magnetic fields. Free radicals have recently been implicated in the biological effects of extremely low frequency (ELF) magnetic fields. Experiments are designed to investigate the involvement of free radicals in magnetic field- induced DNA strand breaks in cells. This proposed research has the following specific aims: (1) To further confirm the blocking effect of melatonin on magnetic field-induced DNA single and double strand breaks in brain cells of rats, a (drug) dose-response study will be carried out. (2) To provide further support for the hypothesis that free radicals are involved in the effect of magnetic fields, animals will be treated with different spin-trap compounds and the vitamin E analog trolox to investigate whether they can block the effects of magnetic fields on DNA strand breaks in rat brain cells. Spin-trap compounds and trolox are efficient free radical scavengers. This is an important new direction in ELF electromagnetic field bioeffect research because DNA damage is closely related to human health risk. Particularly, DNA damage in brain cells could affect neurological functions and also possibly lead to carcinogenesis and neurodegenerative diseases. It is hoped that data from this proposed research will help in identifying possible causal connections of exposure to power frequency magnetic fields and biological effects and also in the hazard assessment of power frequency electromagnetic fields.